Problem: Before the previous stop there were 74 people riding on a train. 50 people ended up getting off at the stop. How many people are riding the train now?
Explanation: The number riding the train now is the difference between the number who were riding and the number who got off at the previous stop. The difference is $74 - 50$ people on the train. $74 - 50 = 24$ people are on the train.